How Much Magnesium Per Day? Dosage by Age, Sex & Goal for Canada (2026)
Quick answer
For most adults, the supplemental dose is 200–350 mg of elemental magnesium a day, taken with food. That stays inside the 350 mg upper limit for magnesium from supplements, and tops up the 310–420 mg a day you need from food and pills together.
One catch nobody mentions: we read the Supplement Facts panel of 833 magnesium labels. The median serving is 250 mg — but follow the label's own directions and the median day comes to 399 mg, above the 350 mg limit.The numbers are below.
A well-evidenced way to start: Nutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day — 200 mg a capsule, so one capsule is a starting dose and two is the trial dose.
Informational summary of NIH guidance and published clinical research — not medical advice. Talk to a clinician for personalised dosing, especially with kidney disease.
Know your dose? See the best magnesium picks at that dose →
How Much Magnesium Per Day?
Adult women need 310–320 mg of magnesium per day and adult men need 400–420 mg, from all sources combined (NIH RDA). Because diet typically covers only part of that, most people supplement with 200–350 mg of elemental magnesium — the range that stays under the ceiling. Trials for specific conditions used more than that, deliberately; those doses are marked as such in the table below.
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Half of magnesium bottles can't deliver a studied dose in one serving. NIH DSLD label census, 825 labels, Aug 2026
Check yours — what does the label say?
Oxide is on 244 of those labels and about 4% of it is absorbed (PMID 11794633): roughly 16 mg of usable magnesium against a 200-400 mg dose. The number on the front is not what you get.
200 mg elemental glycinate per capsule. One capsule, or two for 400 mg:
Nutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count · $0.33/day →Find your magnesium dose
Answer four questions for a personalised target based on the RDA and the clinical trial doses below. It's an estimate, not a prescription — a serum test and your clinician have the final say.
Recommended Daily Allowance (RDA)
These are the total daily magnesium needs from all sources (food + supplements), set by the National Institutes of Health:
| Age Group | Male | Female | Pregnant | Lactating |
|---|---|---|---|---|
| 1-3 years | 80 mg | 80 mg | — | — |
| 4-8 years | 130 mg | 130 mg | — | — |
| 9-13 years | 240 mg | 240 mg | — | — |
| 14-18 years | 410 mg | 360 mg | 400 mg | 360 mg |
| 19-30 years | 400 mg | 310 mg | 350 mg | 310 mg |
| 31+ years | 420 mg | 320 mg | 360 mg | 320 mg |
Source: NIH Office of Dietary Supplements
Want a smaller, Health Canada licensed starting dose? Natural Factors Magnesium Bisglycinate 200 mg Powder, 120g$0.88/day is Health Canada NPN 80091128 at 200 mg — the low end of the typical range.
Clinical Trial Dosages by Condition
These are the elemental magnesium doses used in clinical trials that showed positive results. They represent the amounts actually studied, not manufacturer marketing claims — and the trial durations below are exactly what our how long does magnesium take to work guide walks through in detail, since dose and timeline are two different questions.
| Condition | Dose Studied | Preferred Form | Timing | Evidence |
|---|---|---|---|---|
| Sleep quality | 320-500 mg/day | GlycinateNutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day — 400 mg in two capsules | 30-60 min before bed | Meta-analysis: -17 min sleep onset latency (Mah 2021 meta-analysis, PMID: 33865376) |
| Anxiety / stress | 300-450 mg/day | GlycinateNutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day — 400 mg in two capsules | With meals or before bed | Systematic review of 18 studies (Boyle 2017 systematic review, PMID: 28445426) |
| Migraine prevention | 400-600 mg/day | Citrate or OxideNOW Magnesium Citrate 200 mg (250 Tablets)$0.32/day — the form the migraine trials used | Divided into 2 daily doses | AAN Level B recommendation (Chiu 2016 meta-analysis, PMID: 26752497) |
| Blood pressure | 300-500 mg/day | Any well-absorbed formNutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day | With meals | Meta-analysis of 34 trials: -2 mmHg SBP (Zhang 2016 meta-analysis, PMID: 27402922) |
| Muscle cramps | 300-400 mg/day | Citrate or GlycinateNutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day | Before bed (for nocturnal cramps) | Mixed — Cochrane review shows limited benefit (Garrison 2020 Cochrane review, PMID: 32956536) |
| Cognitive function | 1,500-2,000 mg/day (L-threonate compound) | L-Threonate (Magtein)NOW Magtein Magnesium L-Threonate (90 Veg Capsules)$1.75/day — priced at the 2 g compound dose | Divided into 2 doses | RCT: improved cognition p=0.043 |
| General deficiency | 200-400 mg/day | Glycinate or CitrateNutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day | With meals | NIH ODS recommendation (Zhao 2020 meta-analysis, PMID: 31758631) |
For sleep or anxiety, a well-absorbed glycinate: Nutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day. For migraine prevention or constipation, trials specifically used citrate — NOW Magnesium Citrate 200 mg (250 Tablets)$0.32/day.
Understanding Elemental vs Compound Weight
This is the most common source of dosing confusion. Supplement labels may list either the elemental magnesium or the total compound weight:
Gummies are where this bites hardest: a “600 mg” gummy label can carry 70 mg of elemental magnesium, and no magnesium gummy label we read reaches 300 mg a day.
| Item | Value (%) |
|---|---|
| Oxide | 60% |
| Citrate | 16% |
| Malate | 15% |
| Glycinate | 14% |
| Taurate | 9% |
| Threonate | 7.2% |
| Compound | % Elemental Mg | To get 400mg elemental Mg, you need: |
|---|---|---|
| Magnesium Oxide | 60% | ~670 mg of compound |
| Magnesium Citrate | 16% | ~2,500 mg of compound |
| Magnesium Glycinate | 14% | ~2,850 mg of compound |
| Magnesium L-Threonate | 7.2% | ~5,550 mg of compound |
| Magnesium Taurate | 9% | ~4,450 mg of compound |
| Magnesium Malate | 15% | ~2,670 mg of compound |
How to read the label: Look at the Supplement Facts panel for the line that says "Magnesium" followed by the form in parentheses (e.g., "Magnesium (as Magnesium Glycinate) ... 400 mg"). The number before "mg" is the elemental magnesium — that's the number that matters for dosing.
Want to dial in an exact elemental amount instead of rounding to a fixed capsule dose? A powder lets you measure it: Natural Factors Magnesium Bisglycinate 200 mg Powder, 120g$0.88/day.
When to Take Magnesium
- For sleep: Take magnesium glycinate 30-60 minutes before bed. The glycine component takes effect relatively quickly.
- For general supplementation: Take with a meal. Food improves absorption and reduces the chance of digestive side effects.
- For constipation: Magnesium citrate can be taken morning or evening. Taking it on an empty stomach increases the laxative effect. Our top citrate pick: NOW Magnesium Citrate 200 mg (250 Tablets)$0.32/day.
- Split dosing: If you go above the everyday ceiling (e.g., a trial dose for migraine), split into 2 doses to improve absorption and reduce GI effects.
- Drug separation: If you take antibiotics (tetracyclines, quinolones) or bisphosphonates, take magnesium at least 2 hours before or 4-6 hours after.
Original research · Verified Supplement Data
What the label tells you to take
We read the Supplement Facts panel of 833 on-market magnesium labels in the NIH Dietary Supplement Label Database, and multiplied each serving by the maximum daily servings the label directs. That product — not the number on the front of the bottle — is the dose the label instructs.
The median serving on these labels is 250 mg; taken as directed, the median comes to 399 mg a day, above the 350 mg upper limit for supplemental magnesium. The share of labels over that limit moved by more than 8 points between the two halves of our sample, so we do not print it.
- On the market
- 39,884
- Panels read
- 833
- Declaring a dose
- 825
- Stating a schedule
- 826
- Dose & schedule both
- 779
| Measure | 10th pct | Median | 90th pct |
|---|---|---|---|
| Per serving | 100 mg | 250mg | 500 mg |
| As the label directs, per day | — | 399mg | 500 mg |
| Servings per day | Labels | Share |
|---|---|---|
| 1 | 592 | 72% |
| 2 | 141 | 17% |
| 3 | 76 | 9% |
| 4 | 15 | 2% |
| 5 | 1 | <1% |
| 6 | 1 | <1% |
| Form | Labels | Median | 90th pct |
|---|---|---|---|
| Citrate | 376 | 250mg | 500 mg |
| Oxide | 145 | 300mg | 500 mg |
| Glycinate | 102 | 233mg | 400 mg |
| Malate | 40 | 355mg | 480 mg |
| Aspartate | 27 | 133mg | 400 mg |
| Dose on the panel | Labels | Share |
|---|---|---|
| At or below the 420 mg RDA | 705 | 85% |
| Above the 420 mg RDA | 295 | 36% |
Withheld: the share of labels at or above the upper limit did not hold when the census was split in half, so no figure is printed for it.
Which form the market actually sells
- Magnesium Citrate 44%
- Magnesium Oxide 30%
- Magnesium Aspartate 10%
- Magnesium Glycinate 8%
- Magnesium Malate 8%
Share of 805 chemical-form declarations across 833 labels — a single panel can name more than one.
What this means: The advice every guide ends on — follow the directions on the label — is where the problem starts. Per serving these products look compliant: a median of 250 mg against that ceiling. It is the directions that push them over, because a label that says "take two capsules twice daily" is prescribing four servings, and that multiplication happens nowhere on the front of the bottle. Read the Supplement Facts panel, then check how many servings a day it tells you to take, and multiply. The second number is your dose.
What to look for on the shelf
Two numbers on the panel, not one: the elemental magnesium per serving, and the servings a day it directs. Multiply them and keep the answer at or under 350 mg for everyday use. A 200 mg serving taken once clears that easily, which is why the picks below are dosed where they are — Natural Factors Magnesium Bisglycinate 200 mg Powder, 120g is 200 mg a serving and Health Canada NPN 80091128.
What this cannot tell you: This measures what labels declare and direct, not what is in the capsule and not what you absorb. It cannot tell you whether a product contains what it says — that needs assay testing, which DSLD does not do. Exceeding the supplemental limit is also not a poisoning risk in a healthy adult with normal kidney function; it usually means loose stools. It matters more if you have reduced kidney function, where magnesium clearance falls.
Source: NIH Dietary Supplement Label Database (DSLD) v9, read 2026-08-29. Of 6 properties tested against the sample, 3 held independently in both halves of the read order — and only those are claimed here.
Why the trials used more than the limit
You have now seen two numbers that look like they disagree. The NIH sets a Tolerable Upper Intake Level of 350 mg/day for supplemental magnesium, and the trials in the table above ran at 300–500 mg. Both are correct, and the difference between them is the most useful thing on this page.
The ceiling is not a toxicity threshold. It is the dose at which magnesium reliably starts causing diarrhea in healthy adults — an unabsorbed dose pulling water into the gut, not poisoning. The NIH set it there because that is the point where an ordinary person taking a supplement unsupervised starts having a bad time. A migraine trial running at 600 mg with a clinician watching is accepting that side effect on purpose, in exchange for an effect the lower dose does not produce.
Which means the ceiling is the right number for you and the trial dose is not, unless someone is supervising you. It also means overshooting is uncomfortable rather than dangerous — with one real exception.
- Food is exempt. The limit covers supplements and magnesium-containing medications only. Dietary magnesium has no upper limit; your body regulates absorption from food.
- Kidney disease is the exception that matters. Magnesium clears through the kidneys, so reduced function turns an uncomfortable dose into a genuinely risky one. If your eGFR is below 60, the ceiling above does not apply to you — ask your doctor for a number.
- Real toxicity is rare and needs a much bigger dose. Hypermagnesemia — nausea, low blood pressure, facial flushing, muscle weakness, and in severe cases breathing difficulty or cardiac arrest — generally requires doses above 5,000 mg or existing renal failure.
- Split the dose if you go high. Two smaller doses with food are absorbed better and are gentler on the gut than one large one, which is how the trials gave it.
How Much Magnesium Are You Getting from Food?
Most people get 250-350mg/day from food — below the RDA for most adults. The best dietary sources:
- Pumpkin seeds (1 oz): 156 mg
- Spinach (1 cup cooked): 157 mg
- Dark chocolate (1 oz, 70-85%): 65 mg
- Almonds (1 oz): 80 mg
- Black beans (1/2 cup): 60 mg
- Avocado (1 medium): 58 mg
- Brown rice (1 cup cooked): 84 mg
If you eat a magnesium-rich diet and hit ~300mg from food, supplementing with 100-200mg may be sufficient. If your diet is low in these foods, 300–350 mg supplemental may be appropriate. A healthcare provider can test serum magnesium levels, though this test only reflects ~1% of total body magnesium — some clinicians order an RBC magnesium test instead, though how well-validated that alternative actually is may surprise you.
Best magnesium to hit your dose
Most of the trials above used glycinate — well absorbed and gentle on the stomach. These three cover the 200–350 mg everyday range, ranked by cost per effective dose:
200 mg a capsule: two capsules make the full 400 mg trial dose. Well absorbed, gentle on the stomach.
Health Canada licensed (Health Canada NPN 80091128); powder lets you measure the exact elemental amount.
Lowest cost per dose of the glycinates we carry.
Compare every pick on the magnesium glycinate page or the full best-magnesium ranking.
Frequently Asked Questions
How much magnesium should I take per day?
The RDA is 400-420mg/day for men and 310-320mg/day for women, and that figure covers food and supplements together. For a supplement on its own, 200-350mg of elemental magnesium is the everyday range, because 350mg is the NIH upper limit for supplemental magnesium specifically. Trials for migraine and sleep used more, under supervision.
When is the best time to take magnesium?
It depends on the form and your goal — glycinate before bed for sleep, citrate in the morning for digestion, always with food. See our full best time to take magnesium guide.
Can you take too much magnesium?
The supplemental upper limit is 350mg/day (NIH). Exceeding this primarily causes diarrhea in healthy adults. Dangerous toxicity requires very high doses or kidney disease. Magnesium glycinate is usually reported as the form least likely to cause GI side effects, though no trial has compared forms at the same elemental dose.
What's the difference between elemental magnesium and compound weight?
Magnesium supplements are magnesium bonded to another molecule. "Elemental magnesium" is the actual Mg content your body uses. A 2,000mg magnesium glycinate capsule may contain only ~280mg elemental Mg. Always check the Supplement Facts label for the elemental amount.
How much magnesium should older adults (seniors) take?
The RDA doesn't rise with age — it stays 420mg/day for men and 320mg/day for women over 30. Full breakdown: how much magnesium for seniors.
How much magnesium should a woman take per day?
The RDA for adult women is 310mg/day (ages 19-30) or 320mg/day (31+), rising in pregnancy. Full breakdown: how much magnesium per day for women.
How much magnesium is safe during pregnancy?
The pregnancy RDA is 350-360mg/day for women 19 and older (400mg for ages 14-18), from all sources. Magnesium is generally considered safe in pregnancy and is sometimes used for leg cramps, but supplemental magnesium should stay at or below the 350mg/day upper limit unless an obstetrician advises otherwise. Always clear supplements with your prenatal provider.
Bottom line: most people do well on Nutritionn Magnesium Glycinate 200mg Capsules, Pure Bisglycinate, 300 Count$0.33/day. If constipation is what brought you here, trials used citrate — NOW Magnesium Citrate 200 mg (250 Tablets)$0.32/day.
Related Guides
- Magnesium side effects and too much magnesium — diarrhea by form, the 350 mg supplemental UL, and who must be careful
- Magnesium Glycinate: Products & Cost per Dose — Every verified pick, ranked
- Magnesium Forms Compared — Which form to choose for your goal
- Best Magnesium for Sleep — Products ranked by cost per effective dose
- Magnesium for Anxiety — Dosing for anxiety-specific outcomes
- Signs of Magnesium Deficiency — How to know if you need it
- Glycinate vs Citrate — The most common form comparison question
- How Much Magnesium for Seniors? — Same RDA, bigger safety margin after 65
- How Much Magnesium for Women? — Full RDA table by age, plus pregnancy
- How Long Does Magnesium Take to Work? — What the trials actually timed, by goal
- RBC Magnesium Test — What the evidence for the "better" test actually shows
- Vitamin D Dosage Guide — If supplementing both; magnesium is needed for vitamin D conversion
- All Magnesium Guides
Sources
- NIH Office of Dietary Supplements. "Magnesium: Fact Sheet for Health Professionals." ods.od.nih.gov
- Mah J, Pitre T. "Oral magnesium supplementation for insomnia in older adults." BMC Complement Med Ther. 2021;21(1):125. PMID: 33865376
- Firoz M, Graber M. "Bioavailability of US commercial magnesium preparations." Magnes Res. 2001;14(4):257-62. PMID: 11794633
- U.S. Department of Agriculture FoodData Central. fdc.nal.usda.gov
- Khalid S, et al. “Effects of magnesium and potassium supplementation on insomnia and sleep hormones in patients with diabetes mellitus.” Frontiers in endocrinology. 2024. PMID: 39534260
- Boyle NB, et al. “The Effects of Magnesium Supplementation on Subjective Anxiety and Stress-A Systematic Review.” Nutrients. 2017. PMID: 28445426
- McCabe D, et al. “The impact of essential fatty acid, B vitamins, vitamin C, magnesium and zinc supplementation on stress levels in women: a systematic review.” JBI database of systematic reviews and implementation reports. 2017. PMID: 28178022
- Talandashti MK, et al. “Effects of selected dietary supplements on migraine prophylaxis: A systematic review and dose-response meta-analysis of randomized controlled trials.” Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology. 2025. PMID: 39404918
- Chiu HY, et al. “Effects of Intravenous and Oral Magnesium on Reducing Migraine: A Meta-analysis of Randomized Controlled Trials.” Pain physician. 2016. PMID: 26752497
- Argeros Z, et al. “Magnesium Supplementation and Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.” Hypertension (Dallas, Tex. : 1979). 2025. PMID: 41000008
- Zhang X, et al. “Effects of Magnesium Supplementation on Blood Pressure: A Meta-Analysis of Randomized Double-Blind Placebo-Controlled Trials.” Hypertension (Dallas, Tex. : 1979). 2016. PMID: 27402922
- Bartlett HE, et al. “Nutritional supplementation for type 2 diabetes: a systematic review.” Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists). 2008. PMID: 19076553
- Drenthen LCA, et al. “Oral magnesium supplementation does not affect insulin sensitivity in people with insulin-treated type 2 diabetes and a low serum magnesium: a randomised controlled trial.” Diabetologia. 2024. PMID: 37922013
- Noah L, et al. “Effect of magnesium and vitamin B6 supplementation on mental health and quality of life in stressed healthy adults: Post-hoc analysis of a randomised controlled trial.” Stress and health : journal of the International Society for the Investigation of Stress. 2021. PMID: 33864354
- Tarleton EK, et al. “Role of magnesium supplementation in the treatment of depression: A randomized clinical trial.” PloS one. 2017. PMID: 28654669
- Garrison SR, et al. “Magnesium for skeletal muscle cramps.” The Cochrane database of systematic reviews. 2020. PMID: 32956536
- Liu J, et al. “Effect of oral magnesium supplementation for relieving leg cramps during pregnancy: A meta-analysis of randomized controlled trials.” Taiwanese journal of obstetrics & gynecology. 2021. PMID: 34247796
- Robinson J, et al. “Effect of nutritional interventions on the psychological symptoms of premenstrual syndrome in women of reproductive age: a systematic review of randomized controlled trials.” Nutrition reviews. 2025. PMID: 38684926
- van Die MD, et al. “Vitex agnus-castus extracts for female reproductive disorders: a systematic review of clinical trials.” Planta medica. 2013. PMID: 23136064
- Morishita D, et al. “Senna Versus Magnesium Oxide for the Treatment of Chronic Constipation: A Randomized, Placebo-Controlled Trial.” The American journal of gastroenterology. 2021. PMID: 32969946
- van der Schoot A, et al. “The effect of food, vitamin, or mineral supplements on chronic constipation in adults: A systematic review and meta-analysis of randomized controlled trials.” Neurogastroenterology and motility. 2023. PMID: 37243443
- Tarsitano MG, et al. “Effects of magnesium supplementation on muscle soreness in different type of physical activities: a systematic review.” Journal of translational medicine. 2024. PMID: 38970118
- Heffernan SM, et al. “The Role of Mineral and Trace Element Supplementation in Exercise and Athletic Performance: A Systematic Review.” Nutrients. 2019. PMID: 30909645